This is available. I want you to refer to couple of places in UM6.3/6.4, and then you can make a decision where you want to look at it to get this data.
Reports - We have a report called "Aggregate Capacity and Utilization" that shows Total / Used/ Available/ Overcommitted capacity and Growth rate. This report is not showing 'Committed capacity'.
If you are interested to see 'Committed capacity', you can get them in Aggregates inventory (Storage -> Aggregates). This shows Total / Used/ Available/ Committed capacity.
Regards,
Saravanan